As protests continued Tuesday over the death of an Arunachal Pradesh student, Prime Minister Manmohan Singh condemned the attack as "tragic and shameful" while Delhi Chief Minister Arvind Kejriwal joined the demonstrators at the city centre.

A delegation of northeast leaders and activists also met Home Minister Sushilkumar Shinde and demanded a judicial probe into the matter and a law against racism.

In a related development, a Delhi court sent the three men - Sunder Singh, Pawan Farmania and Farman - arrested in connection with Nido Tania's death to judicial custody till Feb 18.

Terming the attack on 19-year-old Tania, son of Arunchal Pradesh legislator Nido Pavitra, as "most condemnable", Manmohan Singh said "every possible effort" would be made to punish the guilty.

In a statement, the prime minister said: "The attack on Nido Tania, the student from Arunachal Pradesh, is most condemnable. While the actual cause of Nido Tania's death will be known only after the autopsy report is received, the violence which preceded his demise is tragic and shameful."

He also said people from other parts of the country like the northeast are as much a part of the city as anyone else.

"All citizens need to work together to ensure that our brothers and sisters from northeast feel safe and secure in Delhi," he said.

Joining the protestors from the northeast at Jantar Mantar, Kejriwal assured them speedy justice in the case.

"The magisterial enquiry will be over within 3-4 weeks and the truth will be revealed. If the policemen are also involved, we will come to know that too," he said at the protest site where demonstration has been on since Sunday.

The chief minister said that magisterial enquiry ordered by the Delhi government was important as police could have "hushed up" the case.

"Nido's fight is the fight of every Delhiite. It's the fight of every countrymen. We all have to unite to punish the culprits. I am extremely upset by knowing that the FIR (first information report into the incident) was filed two days after the incident.

"This means that if you (protestors) had not united, the FIR would not have been filed. This is very strange. This is our fundamental right," he said.

"We want this place to be safe for women and northeastern people," said Kejriwal, who was accompanied by his cabinet colleague Manish Sisodia.

Tania died last week after he was beaten up by shopkeepers in a south Delhi market following a quarrel over his appearance and clothing. He died in a hospital Jan 30. The victim's friends say it was a racial attack.

Various organisations and students from the northeastern states, demanding justice over Tania's killing, have been holding protests in the city. One group has been camping in Jantar Mantar.

Minister of State for Minority Affairs Ninong Ering, who is an MP from Arunachal Pradesh, led a delegation of activists and students from northeast to the prime minister and Shinde.

On Monday, Ering led a similar delegation to meet Congress vice president Rahul Gandhi who assured speedy justice.

The group also asked Shinde to enact a law against racism. "I think the home minister has agreed to that. We also felt that this case is racial in nature."

The prime minister also said that his "government will make every possible effort to punish the guilty and to provide effective protection to students and citizens from other parts of the country, especially the northeast, who visit or reside in Delhi."

He stressed that every Indian should ensure that fellow citizens from the northeast feel safe and "every part of the country welcomes them, especially New Delhi, which is the national capital" and a "diverse and vibrant city, enriched by people from all over the country who have made it their home".

"What is at stake is human values, amity in society, and the unity and integrity of the country," he added.